/Engine/Plugins/Runtime/MeshModelingToolset/Source/MeshModelingTools/Public/EditMeshPolygonsTool.h
Inset the current set of selected faces. Click in viewport to confirm inset distance.
[UFUNCTION](Programming/UnrealArchitecture/Reference/Functions)(CallInEditor, Category=TriangleEdits, Meta=(DisplayName="Inset", DisplayPriority=2)) void Inset()